3.4.1.5 Dissociation Curves Flashcards
Describe the structure of haemoglobin
Globular protein, water soluble, consists of 4 subunits - 2 alpha, 2 beta polypeptide chains. Each subunit has a haem group which associates with one oxygen molecule
What is the equation for oxyhaemoglobin
Hb + 4O2 <-> HbO8
Define partial pressure
The pressure exerted by an individual gas in a mixture
Describe the role of haemoglobin
Present in RBCs, oxygen molecules bind to the haem groups and are carried around body to where they were needed in respiring tissues
What are 3 factors that affect oxygen-haemoglobin binding
Partial pressure/concentration of oxygen
Partial pressure/concentration of carbon dioxide
Saturation of haemoglobin with oxygen
How does partial pressure of oxygen affect oxygen-haemoglobin binding
As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin
How does partial pressure of carbon dioxide affect oxygen-haemoglobin binding. And what is this effect known as
As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape, the affinity of haemoglobin for oxygen decreases, so more oxygen is unloaded from haemoglobin at same pO2, known as Bohr effect
How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding
It is hard for the first oxygen oxygen to bind, once it does, it causes other haem groups to open up to make it easier for the second and third molecules to bind, known as cooperative binding. Then it is harder for fourth oxygen molecule to bind as you need high pO2 for all 4 haem groups to be saturated
What does haemoglobin do in blood plasma at lungs
Oxygen diffuses into blood plasma, increased pO2 of blood plasma, increased Hb affinity for oxygen, association/loading of oxygen
Hb + 4O2 -> HbO8
What does haemoglobin do in blood plasma at respiring tissue like muscle cells
Oxygen diffuses into respiring tissue, decreased pO2 of blood plasma, decreases Hb affinity for oxygen, dissociation/unloading of oxygen
HbO8 -> Hb + 4O2
How is rate of aerobic respiration maintained to help tissue function more efficiently
Small increase in respiration -> small drop in pO2 of blood -> large drop in % saturation of Hb therefore more oxygen supplied to tissues therefore increased respiration rate is maintained
What does a dissociation curve shift to the right mean
Bohr effect (high pCO2)
What does a dissociation curve shift to the left mean
In low pO2 conditions, Hb can still associate with a lot of O2 therefore can still achieve high % saturation levels at low pO2 so oxygen can be unloaded to tissues at low pO2 to maintain aerobic respiration even in low O2 environments ONLY LLAMA AND FOETUS
